fix(auth): stop dropping the user identifier from localized sign-in labels

[demolaf]

• Related to fix(auth)!: add an Android Lint workflow and gate the Kotlin modules on it #2498

55 locales declared fui_signed_in_as without the %1$s that the base string and DefaultAuthUIStringProvider both expect, so users in those locales saw a bare "Signed in as" with nobody named. Every locale now carries the argument, placed where that language puts it.

That, plus the localization findings that needed no translator, takes auth/lint-baseline.xml from 180 entries to 55:

• values/strings.xml: literal ... becomes …, which the locales already use. One of those strings also held a format specifier, and that pairing is what crashed TypographyDetector on lint's first run here, so fixing the text removes the trigger rather than baselining around it.
• The Romance locales that require a CLDR many plural get one, derived from each file's own other text.
• The 14 AuthException messages that ship empty become translatable="false" — they are override hooks that fall back to the Firebase SDK message, so there is no source text to translate.
• PluralsCandidate is suppressed with tools:ignore on the four declarations that trigger it, rather than disabled for the module — minimumPasswordLength is an unbounded Int, so "at least 1 characters long" is reachable, and the check still needs to guard every other string.

What stays baselined is 43 MissingTranslation findings, real UI copy the Compose rewrite never sent for translation, plus 12 Compose findings tracked separately.

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Maintainer note: Fixes internal CPRN-432

[gemini-code-assist]

Code Review

This pull request configures and integrates Android Lint checks across modules, introducing a repo-wide lintAll task, updating the CI build script, and documenting the linting policy. It also includes various bug fixes and optimizations, such as optimizing QR code generation to reduce JNI crossings, refining coroutine cancellation in AuthFlowController, updating localized strings with proper placeholders, and adding nullability annotations in the paging source. Feedback suggests explicitly validating the non-null Query parameter in DatabasePagingSource using Objects.requireNonNull to prevent potential null pointer exceptions.